[gnome-online-accounts/wip/rishi/ensure-credentials: 3/3] daemon: Enqueue EnsureCredentials calls instead of firing them at once

[Debarshi Ray <debarshir src gnome org>]

commit 32244fb2022d15c53a1af1b9437817f345353b8d
Author: Debarshi Ray <debarshir gnome org>
Date:   Wed Nov 25 17:45:39 2015 +0100

    daemon: Enqueue EnsureCredentials calls instead of firing them at once
    
    It is not a good idea to fire a, possibly, large number of asynchronous
    network operations all at once. Earlier versions of GLib, where the
    thread pool for asynchronous operations had a limit of 10 threads,
    might deadlock if all 10 threaded asynchronous operations are waiting
    for another operation to finish. More recent versions of GLib will
    slowly grow the thread pool to avoid the deadlock, but then we would be
    hoarding network resources.
    
    Having a queue of pending operations also lets us implement some
    optimizations. We can reduce the number of times we need to hit the
    network by coalescing requests against the same GoaObject. Secondly,
    we can give higher priority to requests that originated over D-Bus from
    an actual client as opposed to those that originated internally due to
    potential network changes.

 src/daemon/goadaemon.c |  109 +++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 89 insertions(+), 20 deletions(-)
---
diff --git a/src/daemon/goadaemon.c b/src/daemon/goadaemon.c
index 02f886f..6f029fd 100644
--- a/src/daemon/goadaemon.c
+++ b/src/daemon/goadaemon.c
@@ -42,6 +42,9 @@ struct _GoaDaemon
 
   GoaManager *manager;
 
+  GQueue *ensure_credentials_queue;
+  gboolean ensure_credentials_running;
+
   guint config_timeout_id;
   guint credentials_timeout_id;
 };
@@ -74,6 +77,8 @@ static gboolean on_account_handle_ensure_credentials (GoaAccount            *acc
                                                       GDBusMethodInvocation *invocation,
                                                       gpointer               user_data);
 
+static void ensure_credentials_queue_check (GoaDaemon *self);
+
 static void goa_daemon_check_credentials (GoaDaemon *self);
 static void goa_daemon_reload_configuration (GoaDaemon *self);
 
@@ -113,6 +118,7 @@ goa_daemon_finalize (GObject *object)
   g_object_unref (self->manager);
   g_object_unref (self->object_manager);
   g_object_unref (self->connection);
+  g_queue_free_full (self->ensure_credentials_queue, g_object_unref);
 
   G_OBJECT_CLASS (goa_daemon_parent_class)->finalize (object);
 }
@@ -275,6 +281,8 @@ goa_daemon_init (GoaDaemon *self)
                            self,
                            G_CONNECT_SWAPPED);
 
+  self->ensure_credentials_queue = g_queue_new ();
+
   /* Export objects */
   g_dbus_object_manager_server_set_connection (self->object_manager, self->connection);
 
@@ -1166,13 +1174,19 @@ is_authorization_error (GError *error)
 }
 
 static void
-ensure_credentials_cb (GoaProvider   *provider,
-                       GAsyncResult  *res,
-                       gpointer       user_data)
+ensure_credentials_queue_collector (GObject *source_object, GAsyncResult *res, gpointer user_data)
 {
-  EnsureData *data = user_data;
-  gint expires_in;
+  GTask *task = G_TASK (user_data);
+  GoaDaemon *self;
+  EnsureData *data;
+  GoaProvider *provider = GOA_PROVIDER (source_object);
   GError *error;
+  gint expires_in;
+
+  self = GOA_DAEMON (g_task_get_source_object (task));
+  g_assert (task == G_TASK (g_queue_pop_head (self->ensure_credentials_queue)));
+
+  data = g_task_get_task_data (task);
 
   error= NULL;
   if (!goa_provider_ensure_credentials_finish (provider, &expires_in, res, &error))
@@ -1217,7 +1231,49 @@ ensure_credentials_cb (GoaProvider   *provider,
       if (data->invocation != NULL)
         goa_account_complete_ensure_credentials (account, data->invocation, expires_in);
     }
-  ensure_data_unref (data);
+
+  self->ensure_credentials_running = FALSE;
+  ensure_credentials_queue_check (self);
+  g_object_unref (task);
+}
+
+static void
+ensure_credentials_queue_check (GoaDaemon *self)
+{
+  EnsureData *data;
+  GoaAccount *account;
+  GoaProvider *provider = NULL;
+  GTask *task;
+  const gchar *id;
+  const gchar *provider_type;
+
+  if (self->ensure_credentials_running)
+    goto out;
+
+  if (self->ensure_credentials_queue->length == 0)
+    goto out;
+
+  task = G_TASK (g_queue_peek_head (self->ensure_credentials_queue));
+  self->ensure_credentials_running = TRUE;
+
+  data = (EnsureData *) g_task_get_task_data (task);
+  account = goa_object_peek_account (data->object);
+
+  id = goa_account_get_id (account);
+  provider_type = goa_account_get_provider_type (account);
+  g_debug ("Handling EnsureCredentials for account (%s, %s)", provider_type, id);
+
+  provider = goa_provider_get_for_provider_type (provider_type);
+  g_assert_nonnull (provider);
+
+  goa_provider_ensure_credentials (provider,
+                                   data->object,
+                                   NULL, /* GCancellable */
+                                   ensure_credentials_queue_collector,
+                                   task);
+
+ out:
+  g_clear_object (&provider);
 }
 
 static gboolean
@@ -1226,8 +1282,10 @@ on_account_handle_ensure_credentials (GoaAccount            *account,
                                       gpointer               user_data)
 {
   GoaDaemon *self = GOA_DAEMON (user_data);
-  GoaProvider *provider = NULL;
+  EnsureData *data;
   GoaObject *object;
+  GoaProvider *provider = NULL;
+  GTask *task = NULL;
   const gchar *id;
   const gchar *method_name;
   const gchar *provider_type;
@@ -1235,11 +1293,9 @@ on_account_handle_ensure_credentials (GoaAccount            *account,
   id = goa_account_get_id (account);
   provider_type = goa_account_get_provider_type (account);
   method_name = g_dbus_method_invocation_get_method_name (invocation);
-  g_debug ("Handling %s for account (%s, %s)", method_name, provider_type, id);
+  g_debug ("Received %s for account (%s, %s)", method_name, provider_type, id);
 
-  object = GOA_OBJECT (g_dbus_interface_get_object (G_DBUS_INTERFACE (account)));
   provider = goa_provider_get_for_provider_type (provider_type);
-
   if (provider == NULL)
     {
       g_dbus_method_invocation_return_error (invocation,
@@ -1251,14 +1307,18 @@ on_account_handle_ensure_credentials (GoaAccount            *account,
       goto out;
     }
 
-  goa_provider_ensure_credentials (provider,
-                                   object,
-                                   NULL, /* GCancellable */
-                                   (GAsyncReadyCallback) ensure_credentials_cb,
-                                   ensure_data_new (self, object, invocation));
+  object = GOA_OBJECT (g_dbus_interface_get_object (G_DBUS_INTERFACE (account)));
+  data = ensure_data_new (self, object, invocation);
+
+  task = g_task_new (self, NULL, NULL, NULL);
+  g_task_set_task_data (task, data, (GDestroyNotify) ensure_data_unref);
+  g_queue_push_tail (self->ensure_credentials_queue, g_object_ref (task));
+
+  ensure_credentials_queue_check (self);
 
  out:
   g_clear_object (&provider);
+  g_clear_object (&task);
   return TRUE; /* invocation was handled */
 }
 
@@ -1279,9 +1339,12 @@ goa_daemon_check_credentials (GoaDaemon *self)
   objects = g_dbus_object_manager_get_objects (G_DBUS_OBJECT_MANAGER (self->object_manager));
   for (l = objects; l != NULL; l = l->next)
     {
+      EnsureData *data;
       GoaAccount *account;
       GoaObject *object = GOA_OBJECT (l->data);
       GoaProvider *provider = NULL;
+      GTask *task = NULL;
+      const gchar *id;
       const gchar *provider_type;
 
       account = goa_object_peek_account (object);
@@ -1293,14 +1356,20 @@ goa_daemon_check_credentials (GoaDaemon *self)
       if (provider == NULL)
         continue;
 
-      goa_provider_ensure_credentials (provider,
-                                       object,
-                                       NULL, /* GCancellable */
-                                       (GAsyncReadyCallback) ensure_credentials_cb,
-                                       ensure_data_new (self, object, NULL));
+      id = goa_account_get_id (account);
+      provider_type = goa_account_get_provider_type (account);
+      g_debug ("Calling EnsureCredentials for account (%s, %s)", provider_type, id);
+
+      data = ensure_data_new (self, object, NULL);
+
+      task = g_task_new (self, NULL, NULL, NULL);
+      g_task_set_task_data (task, data, (GDestroyNotify) ensure_data_unref);
+      g_queue_push_tail (self->ensure_credentials_queue, g_object_ref (task));
 
       g_clear_object (&provider);
+      g_clear_object (&task);
     }
 
+  ensure_credentials_queue_check (self);
   g_list_free_full (objects, g_object_unref);
 }